One challenge in robotics is that of determining the 6 degree of freedom (6-DOF) state of a platform within an environment. By 6-DOF state, we refer to both the 3-DOF location of a platform in Cartesian X-Y-Z space and the 3-DOF pose. The X-Y-Z location may be computed in reference to an objective frame of reference, which may be fixed as Earth-bound or attached to another frame of reference. The 3-DOF pose may be expressed as Euler angles (roll, pitch, and yaw) or in quaternions. In this document, we shall refer to the act of determining the 6-DOF state of a platform as the process of “localization”.
There are a number of techniques for localizing a platform within an environment. SLAM (simultaneous localization and mapping) techniques have advanced in recent years. However, they generally require substantial processing power and the use of heavy sensor equipment. Such algorithms are also too slow for many applications. Other techniques involve the use of external motion capture systems, in which an environment is populated with cameras that view an object from many angles and from this information compute 6-DOF state. Example equipment includes system manufactured by Optitrak and Vicon. Such techniques are able to produce accurate and fast state estimations, but are expensive and require the environment to be populated with large numbers of cameras.
Another set of techniques involves the use of external beacons which are mounted at known locations in an environment. Such beacons may emit light or RF pulses, which may then be received by a receiver on a platform. Techniques such as time of flight (TOF) and angle of arrival (AOA) may then be used to determine an objects location. The invention described herein is of this latter category.